Unionized maintenance workers, housekeepers, and nursing assistants at the Mayo Clinic hospital in Albert Lea went on a one-day strike on Tuesday to protest what they described as one-sided contract bargaining.

But when they tried to report for their jobs before 6 a.m. Wednesday morning, Mayo sent security to bar them from entry, making good on an earlier promise to replace striking workers with general contractors for one week, including Christmas. Only the six maintenance workers were allowed through.

The Service Employees International Union says that as far as they know, this is the first healthcare lockout in Minnesota history. The union and its allies have raised funds to replace wages the workers would have received.

"Mayo has decided to value replacement workers from outside of the community over dedicated employees with hundreds of years experience, including multiple who have worked at the hospital for a quarter century," SEIU said in a statement. "They made this decision even though it meant a Christmas lockout that would upend the lives of families in the heart of the holiday season."

Workers have promised to picket for the rest of the week. They complain that Mayo is seeking the ability to retool benefits at will, as well as to subcontract away maintenance jobs.These disagreements have been standing in the way of ratifying a new contract for more than a year.

"They've been trying to impose longer hours, cut out a lot more benefits for the part-timers, take insurance away, take away weekend bonuses," says Marlene Baseman, a hospital housekeeper who has been with Mayo for more than 27 years. "Holidays and everything, when they're home with their families, we're here working."

Justin Yost, who worked in the utilities department for 14 years, says he worries what will come if Mayo is able to insert language into the contract that allows easy outsourcing of his job. Maintenance workers like him have been bargaining for more than two years, he says, because the bosses refuse to give them the job security they want.

"For a town like Albert Lea, which is such a small town ... just keeping good-paying jobs down here is important."

Mayo shot back Tuesday, accusing the union of using employees as pawns in a holiday strike. Replacements, who had to be contracted for at least a week, were necessary to avoid interrupting patient care, Mayo said in a statement. Though strikers will not be paid during that time, they will continue to receive health insurance coverage.

"We remain committed to providing fair wages and benefits," Mayo's statement read. "These employees are being offered the same Mayo Clinic benefits package as virtually all other allied health employees, which we strongly believe is better as a whole than the benefits they currently receive."

Picketing workers say they want to see that in writing, but Mayo spokeswoman Ginger Plumbo argues it's hard to discuss anything when the union that represents the majority of the workers who went on strike hasn't returned to the bargaining table since May.

The group representing six maintenance engineers had some sessions in the spring, where they introduced subcontracting language to which Mayo agreed, Plumbo says. Bargaining then lapsed for several months, and when the union returned to the table in the fall, it reneged on its earlier subcontracting proposal.

Mayo is confused by that, Plumbo says, adding that the only changes to benefits over the past few years have been additions.

The next bargaining session between Mayo and SEIU will take place on December 28.